Enterasys Networks 2E253, 2H253, 2H252, 2H258 manual Solving the Problem, Switches 1

Example 3, Filtering Traffic According to a Layer 4 Classification Rule

12.14EXAMPLE 3, FILTERING TRAFFIC ACCORDING TO A LAYER 4 CLASSIFICATION RULE

This example illustrates how to filter out broadcast transmissions at Layer 4 from other parts of a network.

In this example, illustrated in Figure 12-16, Switches S1 and S2 have already been configured and are operating. However, it was discovered that the Routing Information Protocol (RIP) broadcast frames from routers R1 and R2 were flooding the subnetwork of Switches S1 and S2.

Figure 12-16 Example 3, Filtering Traffic According to a Classification

R1

Port 25

S1

Users

R2

Port 25

S2

Users 30691_73

12.14.1 Solving the Problem

To prevent the RIP broadcasts from flooding the users terminals connected to S1 and S2, a new VLAN will be added to each switch, but not assigned to any ports (creating a Null VLAN). Then each switch will be configured with a Layer 4 classification rule that will classify each RIP broadcast frame received on Port 25 of each switch to the Null VLAN. Since the Null VLAN is not associated with any ports, the frame will be dropped and not transmitted out any port.

In this example, the switches have already been configured and operating. The following covers only those steps needed to configure each switch to eliminate the problem.

Switches 1 and 2

Each switch is set as follows:

1.A VLAN is added to the list of VLANs in the Static VLAN Configuration screen and assigned to an FDB ID. In this example, the switch is set as follows:

• VLAN ID 99, FDB ID 99, with a VLAN Name of Null VLAN

12-32VLAN Operation and Network Applications